The questions that keep repeating
"How's the project going?", "Did you get my invoice?", "Do I still have documents to sign?", the same questions come back with every client, eating up time that could go toward actual delivery.
What a portal changes
When the client has direct access to project status, invoices and their documents, most of these questions become unnecessary, the answer's already there, whenever they check.
The less obvious benefit
A portal doesn't just cut down questions, it builds trust too. A client who can check for themselves at any time feels more in control of their own project than one who depends entirely on your replies.
Bottom line
The time saved from fewer status emails adds up quickly at the scale of several simultaneously active clients.